Tobies corp



Patented June 26, 1928.

UNITED STATES PATENT OFFICE. A

GRANT 8. DIAMOND, OF BUFFALO, NEW YORK, ASSIGNOB TO THE ELECTRIC BEFRAG- TORIES 00319., OF BUFFALO, NEW YORK.

REFRACTORY ARTICLE AND MATERIAL AND METHOD OF MAKING THE SAME.

Ho Drawing.

This invention relates to a non-recrystallized, refractory material or ob ect, such as may be employed in making crucibles, furnace bricks, tiles, muflies, arches, pedestals,

linings, covers, and for various other applications where high temperatures are used. Heretofore most of the refractory compositions, particularly for crucibles, have been formed of graphite and a clay, but the life of such articles has been very short and unsatisfactory, particularly in the iron industry, such as in melting iron or steel. Th s short life has been lax-gel due to the chemical action which occurs etween the clay in the crucible and the metal being treated.

The steel or iron dissolves out the silicon in the clay and thus destroys the crucible wall after a short interval of use.

An ob'ect of the invention is to prov de an improve refractory material which will not require finishing in a recrystallized state.

A further object of the invention 18 to provide an improved refractory material which is flexible, durable, non-crack ng, nondisintegrating, non-oxidizing, relatively 1nexpensive, and one which will resist the chemical action of metals, fluxes, and slags.

A further object is to provide an improved method of making refractory materlals and articles.

Other objects and advantages of the 1H- vention will be apparent from the following discussion of the invention.

The basis of the improved refractory material is magnesium oxide. To this oxide I add raphite, preferably in crystalline form. To t e aphite and magnesium oxide I also refera ly add a suitable binder, and if the binder is a carbonizing binder, I also prefer o use a fusion agent.

In referring to magnesium oxide, I intend to include by that expression burnt or calcined, or fused or sintered magnesite or magnesia, or any other material the principal constituent of which is an oxide of magnesium and this material is preferably in powdered form. Magnesium oxide is particularly valuable as an ingredient of refractory materials, due to its high fusion point, its heat conductivity, low coeflicient of thermal expansion, and basic chemical nature.

While any magnesium oxide may be used Application filed September 23, 1926. Serial No. 137,383.

I prefer to use the fused magnesium oxide. The unfused magnesite when heated while in service will have a normal thermal expan- SlOIl up to about 2800 F. and then will shrink under continuing or rising heat as it nears the softening point. ()n the other hand, the fused magnesium oxide does not have the shrinking defect and has normal thermal expansion up to the melting oint and is therefore preferable to the un used ma nesite.

he graphite is preferably in the crystalline form which corresponds tothe common flake graphite well known in the various industries, and often referred to as Ceylon, Madagascar, etc. The graphite in itself is a good refractory, but in this mixture it has the additional pro erty of reducing the elasticity required or a cruci 1e refractory. The graphite in this mixture cannot be considered as a binder since it is intended as a refractory ingredient and a permanent part of the refractory.

Any suitable binder may be used but I have found a carbonizin binder to be very satisfactory. Such a binder may be tar, pitch, molasses, dextrin, natural or synthetic resins, etc. The expression carbonizing binder is intended to include any carbonaceous substance which can be obtained in liquid form, and which, when baked, at say from 1000 to 1800 C. under non-oxidizin'g conditions. leaves a residue of carbon. This carbon bond is superior to any other bond for certain types of refractories. It is desirable, however in the use of a carbon bond to also add to the mixture a suitable fusion agent or flux, sometimes called a glaze, in order to protect the bond from oxidation in the use of the refractory material. Other binders which may be used are kaolin, aluminous clays, silicate salts, various oxides, such as calcium oxide, or other suitable binding materials.

The glaze or fusion agent should be metallurgically neutral, such as chemically neutral silicate, and should be so selected that its melting point will be proper for the particular conditions under which the crucible or other refractory material or articles is to be used, such as a melting point between 1500 and 3000 F. Ferrous oxide and sodium carbonate may also be used successfully fractor as fusin agents, When magnesium oxide and grap ite are used with a carbon binder,

it is also desirable to use a fusion agent or glaze in order to rotect the carbon from oxidation, and whi e all the desired amount of the fusion agent may be mixed with the other ingredients before molding and baking, I prefer to mix art of the fusion agent or glaze with the ot er ingredients prior to baking and then either be ore or after baking, preferably after,-the remainder of the fusion agent or glaze is painted upon the molded refactory object and the latter then rebaked.

The proportions of the different ingredients may be varied to some extent, but the following examples will serve as an indica tion of the proportions which have been found very 'satis actory:

Example I.

Per cent. Magnesium oxide 40 to Cr stalline graphite -1 20 to 40 A inder i Oto 20 Example II.

Per cent. Magnesium oxide 50 Graphite 20 Fusion agent 12 Tar 18 The proportions may also be varied somewhat in accordance with the different uses to which the material or article is to be put. For example, for some refractory sha es it will be necessaryl to than others and t is may be accomplished by varying the fproportion of the graphite. The range 0 variations may be even 10 r cent or moped After the dos ed proportions have been decided u n, the various dry ingredients may be t oroughlg mixed dry, the liquid binder added an mixed therewith, the whole then allowed to age for a suitable period after which the mixture may be presse molded s un, or otherwise formed into the desire s ape and size, and then baked at a temperature of a proximately 1000 C. The articles, after in mg, may be placed in use.

. The refractory material embodying this invention is purel a non-recrystallized rein view 0 the fact that the finished article 18 not a homogeneous, monolithic mass produced by recrystallizing the ingredients at their sublimation temperatures. This non-recrystallized finish is important since it eliminates the ver costly and diflicult temperatures commo y used in making refractories such as magnesia and alundum.

It will be obvious t at variouschanges in the details, which have been herein'described in order to explain the nature of the invention, may be made by those skilled in the have more flexi ility art within the principle and scope of the invention as expressed in the appended claims.

I claim 1. A refractory material comprising a non-recrystallized mixture of fused magnesium oxide and a carbon binder, with a protecting surface glaze.

2. A refractory material comprising a non-recrystallized mixture of fused magnesium oxide, crystalline graphite, a binder, with at protecting surface glaze.

3. A refractory material comprising a non-recrystallized mixture of magnesium oxide, :1. carbon binder, and a fusion agent, which has been heated to a temperature sufficient to convert the fusion agent into a surface glaze and less than approximately 1000 C.

4. A refractory material comprising a non-recrystallized rrixture of magnesium oxide, crystalline graphite, a carbon binder, and a fusion agent.

5. A refractory material containing mag nesium oxide, crystalline graphite, and a binder. y

6. A refractory material comprising magnesium oxide, crystalline graphite, and a. carb on binder.

7. .A refractory material comprising magnesium oxide, crystalline graphite, a carbon binder, and a fusion agent.

8. A refractory material containing fused magnesium oxide, crystalline graphite, and a binder. x

9. A refractory material comprising fused ma esium oxide, crystalline graphite, and a car n binder.

' 10. A refractory material com rising ma esium oxide, cr stalline grap ite, a car n binder, and a usion agent of a silicate salt.

11. A refractory material com rising ma esium oxide, crystalline grap to, a.

bin er, and a fusion agent.

12-. A refractory material comprising a non-recrystallized mixture of magnesium oxide and crystalline graphite,

13. A refractory article com rising a mixture of ma esium oxide, grap ite, a carbon binder an av-fusion agent, which mixture has been heated to approximatel 1000 0. without recrystallization and wit outmaterial oxidation of the binder.

14. A non-recrystallized refractory object containing magnesium oxide, and crystalline graphite.

15. A non-recrystallized refractory object containing magnesium oxide, crystalline gra hite, a carbon binder, and a protecting an ace glaze.

16. The method of making refractory articles which comprises mixing an oxide of magnesium and crystalline graphite with a liquid binder, forming the mixture into the desired articles, and baking the articles at a temperature of approximately 1000 C.

17. The method of making refractory articles which comprises mixing an oxide of magnesium and crystalline graphite with a lhpgnd binder, ageing the mixture for a suita 1e period, forming the mixture into the desired articles and baking the articles at a temperature of approximately 1000 C.

18. The method of making refractory articles which comprises mixing together an oxide of magnesium, crystalline graphite, a fluid carbon binder, and a fusion a t, formi the mixture into the desired artlcles, and ha ing the latter at a temperature of approximately 1000 C.

19. A non-recrystallized, refractory material containing in approximate amounts from to 60 percent magnesium oxide, 20 to 40 percent graphite, and a binder.

20. A non-recrystallized, refractory object containing in approximate percentages percent magnesium oxide, 20 percent of graphite, 12 percent of fusion agent, and 18 percent of tar.

21. Anon-recrystallized, refractory material containing in approximate amounts from 40 to 60 percent magnesium oxide, 20 to 40 percent crystalline graphite, and a binder.

22. A non-recrystallized, refractory material containing in approximate amounts from 40 to 60 percent magnesium oxide, 20 to 40 percent crystalline graphite, and 20 percent binder.

23. A non-recrystallized, refractory material containing in approxlmate amounts from 40 to 60 percent magnesium oxlde, 2O

to 4.0 ercent crystalline graphite, and a carbon inder up to 20 percent.

24. A non-recrystallized, refractory material containing in approximate amounts from 40 to 60 percent magnesium oxide, 20 to 40 percent crystalline graphite, a carbon binder up to 20 percent, and a suitable fusion agent.

25. An improved refractory article containin a mixture of ma nesium oxide, graphite, and a carbon hinder. the magnesium oxide comprises from 40 to 60 percent of the total mixture, and the mixture having been heated to approximately 1000 C. without recrystallization and without material oxidation of the binder.

26. The method of making refractory articles which comprises mixing an oxide of magnesium and crystalline graphite with a carbon binder and a quantity of a glaze, forming the mixture into the articles desired, baking the articles, and applying a coating of further glaze to the articles after they have been formed from the mixtures.

27. The method of making refractory articles which comprises mixing an oxide of magnesium and crystalline graphite with a carbon binder and a uantity of a glaze, forming the mixture into the articles desired, baking the articles, applying to the baked articles a coating of a further quantity of the glaze, and then rebaking them.

28. A crucible having incorporated in its wall along its inner surface a mixture of fused magnesium oxide, crystalline graphite, a carbon binder and a protecting surface glaze.

GRANT S. DIAMOND. 

